Weltec reveals slurry, digestate process to reduce volume by half

German-based Weltec Biopower GmbH recently announced it is offering a slurry and digestate processing system called Kumac to livestock owners and biogas plant operators. The fully automated processing system reduces the volume of liquid manure and digestate by 50 percent through a four-stage procedure where clear water, liquid fertilizer concentrate and valuable solid matter are extracted from the source material.

Weltec developed the Kumac system to address a problem in regions characterized by agriculture that face high accumulation of slurry and digestate, with limited areas suitable for spreading the nutrients. According to the company, in the future, restrictive laws will impose even stricter regulations for handling the nutrient surplus. “Against this background, operators are finding it more and more costly to store and dispose of liquid manure and digestate,” according to Weltec. The company claimed their Kumac processing system represents a sustainable, economic solution for reducing the quantity, thereby improving the transportability and volume of the nutrient surplus.

The first step in the overall process is to separate the solid and liquid matter. Flocculants are added to the liquid manure and digestate during this step. In this way, certain nutrients are fixed, and it becomes easier to separate the solid matter from the liquid phase with the belt filter press. The additives also help alleviate the odorous emissions. The drained solid matter has a dry matter content of about 30 percent, according to the company, and can be used as a fertilizer, compost or litter or, in the case of slurry, as a biogas feedstock.

Following the initial separation of the solid and liquid matter, the remaining liquid phase is passed through a flotation tank in order to separate further small particles and suspended matter. Any remaining solid particles are removed by a fine filter. In the next step, the filtrate traverses a three-stage reverse osmosis process in order to concentrate salts and nutrients. The resulting liquid fertilizer is rich in nitrogen and merely accounts for one quarter of the original volume, the company stated in a release. Half of the treatment products consist of clear water, which can be introduced to the water cycle after being processed in the ion exchanger.

The scalable modular system has the capacity to process 50,000 tons of slurry or digestate a year. If the processing needs increase, a combination of several Kumac lines can be implemented. The Kumac system is highly automated, and efficient use of the final product—half of which consists of drainage water, a quarter of useful solid matter and a quarter of valuable nutrient concentrate—increases the overall efficiency of the Kumac treatment system, the company stated.

Weltec’s Kumac technology has already been deployed at agricultural plants and large biogas plants in Belgium and the Netherlands for almost 10 years, and they said operators are pleased with the reliable, low-maintenance technology and low energy consumption. "Another reason for the positive feedback is that meanwhile, we have further developed the procedure in accordance with operator requirements,” explained Jens Albartus, director of Weltec. The system's reputation is backed by the investigation results of the Dutch Wageningen University and the German Chamber of Agriculture of Lower Saxony that confirm the high functionality and mass balance of the Kumac treatment system, according to Weltec.

Overall, the company said its processing concept is equally suitable for users from different areas, such as pig and cattle owners and biogas plant operators.